Pereyaslav Agreement, Pereyaslav also spelled PerejasŁaw, (Jan. 18 [Jan. 8, Old Style], 1654), act undertaken by the rada (council) of the Cossack army in Ukraine to submit Ukraine to Russian rule, and the acceptance of this act by emissaries of the Russian tsar Alexis; the agreement precipitated a war between Poland and Russia (1654–67).

The hetman of the Zaporozhian Cossacks, Bohdan Khmelnytsky, had been leading a revolt against Polish rule in Ukraine since 1648. In 1651, in the face of a growing threat from Poland and forsaken by his Tatar allies, Khmelnytsky asked the tsar to incorporate Ukraine as an autonomous duchy under Russian protection. The Russians were reluctant to enter into such an agreement, and it was not until October 1653 that a Russian zemsky sobor (“assembly of the land”) approved the request and Alexis sent a delegation, headed by V.V. Buturlin, to the Cossacks.

Only after the Cossacks had suffered a disastrous military defeat (December 1653), however, did the rada receive the Muscovite delegation at Pereyaslav and formally submit to “the tsar’s hand.” Two months later (March 1654), the details of the union were negotiated in Moscow. The Cossacks were granted a large degree of autonomy, and they, as well as other social groups in Ukraine, retained all the rights and privileges they had enjoyed under Polish rule. But the unification of Ukraine with Russia was unacceptable to Poland; a Russo-Polish war (Thirteen Years’ War) broke out and ended with the division of Ukraine between Poland and Russia. See alsoAndrusovo, Truce of.

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(Jan. 30 [Feb. 9, New Style], 1667), long-lasting treaty that ended the Thirteen Years’ War (1654–67) between Russia and Poland for control of Ukraine. In 1654 the Russian government accepted the Pereyaslav Agreement, a proposal to annex Ukraine made by the hetman (military leader) of...

While military operations continued inconclusively, and because Tatar support proved undependable at crucial moments, Khmelnytsky began to search for other allies. In 1654 at Pereyaslav he concluded with Moscow an agreement whose precise nature has generated enormous controversy: Russian historians have emphasized Ukraine’s acceptance of the tsar’s suzerainty, which subsequently legitimized...

In 1654 Khmelnytsky submitted to Tsar Alexis in the Pereyaslav Agreement. Russian historiography characterizes that agreement as the reunification of Ukraine with Russia; the Ukrainians interpret it as an alliance based on expediency. At any rate, war began between Muscovy and the Commonwealth, and Alexis’s armies drove deep into Lithuania. In 1655 they occupied its capital, Wilno. For the...